The present invention relates generally to valves and more specifically to valves as may be used in dental syringes and the like.
For many applications, and in particular dental syringes, a valve is needed which is activated by axially pushing the valve actuator. It is also important for dental applications that the dentist have close control of the fluid flow from the syringe from zero flow to the designed maximum flow of the valve. These two features heretofore have been difficult to reconcile in valves of the prior art. In many valves of the prior art where the valve seal member is moved axially from the valve seat, the entire circumference of the valve is open to accommodate the fluid flow. Accordingly, in this type of prior art valve, it was necessary to maintain close, critical tolerances between the opening of the valve seat and the valve member. Not only is it expensive to maintain such close tolerances as required in such a valve but, the valve member itself must be hardened as any wear reduces the amount of control over the flow which can be exercised by the dentist. All these factors added considerably to the cost of the valve.
The valve of the present invention not only allows for a greater control of flow than valves of the prior art, but also accomplishes this control while utilizing considerably less critical tolerances which in turn greatly reduces cost. Further, since the tolerances are reduced, wear becomes less of a factor so that the life of the valve is prolonged.
Another troublesome problem with dental syringes is that when the actuator is released and the valve closed, some liquid remains and/or drips from the nozzle of the syringe. There is the danger of any fluid, such as water, remaining in the nozzle becoming contaminated and of course any dripping from the nozzle is objectionable in that it wets the exterior of the dental equipment.
In the valve of the present invention, a slight negative pressure is created when the valve actuator is releaased so that when the valve is closed, fluid is drawn from the nozzle and back into the valve housing where there is less likelihood of contaminaation and dripping is prevented.
The aforementioned features of the present invention are accomplished by tilting the valve member on, and with respect to, its seat responsive to the initial axial movement of the valve actuator. This opens only a portion of the total circumference of the valve to fluid flow. Continuing the axial movement of the actuator then drives the entire valve member from its seat to open the entire circumference of the valve to fluid flow. Still further movement of the actuator drives the valve member entirely from the seat to provide the maximum valve opening. On release of the actuator, the valve member is returned to its seat to close the valve. A bias means continues to operate on and move the actuator after the valve member is seated. This provides a suction which draws fluid from the nozzle back into the valve housing.